PROJECT SUMMARY Manganese (Mn) plays an essential role in normal growth and development The Communities Actively Researching Exposure Study (CARES) was built upon community-engaged research practices. Participants reside in three communities with the nation's highest levels of ambient Mn: Marietta and East Liverpool, Ohio, and Southeast Side Chicago, Illinois. The CARES cohort consists of over 600 children and their primary caregiver, with two time-points (ages 7-9 years and ages 13-17 years) of extensive neurodevelopmental outcomes, biomarkers of exposure, and home environmental measures. The CARES has been supported by multiple NIEHS-funded grants and has been instrumental in the training of next generation community- engaged environmental health scientists for over a decade. The cohort has been instrumental in the development of a lab-on-a-chip sensor for blood metals assessment and is currently exploring the impact of Mn on neuroanatomy, function, chemistry, and physiology through magnetic resonance imaging. Through this project, the CARES research team will be able to conduct the following: Aim 1) Maintain the integrity of the CARES cohort by implementing community-engaged research strategies to improve participant retention; Aim 2) Expand CARES to enhance characterization of critical windows of exposure across the lifespan, and assess the role of caregiver, child, and community-level psychosocial factors on the etiology of toxicant-induced neurodevelopmental deficits; and Aim 3) Maintain and enhance biorepository and data management infrastructure and develop methods to implement data sharing. The CARES is the only cohort poised to investigate ambient exposure to Mn and its relationship to brain function in both a pediatric and adolescent population. The proposed cohort retention, enhancement, and maintenance plans will accelerate and sustain the ability of the CARES cohort to investigate the impact of ambient Mn on neurodevelopmental outcomes, inform federal polices related to ambient exposure to Mn, and serve as a valuable resource for environmental health science trainees and scientists across the globe.